Learn how to use this product The RTS Amino Acid Sampler provides ready-to-use stock solutions of 20 individual amino acids that can be labeled and used to replace the amino acids supplied in the RTS 100 (BR BR1400101), RTS 500 (BR BR1400501), or RTS 9000 (BR BR1400301) E. coli HY Kits. Using the RTS 500 or RTS 9000 E. coli HY Kits, protein yields are sufficient in many cases for subsequent use in NMR spectroscopy.